1. Field of the Invention
This invention relates to watt meters. More particularly, this invention relates to instantaneous reading watt meters that measure the rotational speed of the spinning disk of a conventional utility kilowatt-hour meter to then compute the instantaneous power demand.
2. Description of the Background Art
In an era of energy conservation awareness, it is often desirable or necessary to determine the instantaneous electrical power demand of a particular piece of equipment or of an entire facility. Electrical power demand is expressed in watts or kilowatts, and should be clearly distinguished from electrical energy consumption that is expressed in watt-hours or kilowatt-hours.
Presently, there exist many types of watt meters that are designed to read instantaneous electrical power demand. However, such watt meters require a connection of current shunts or current transformers on each of the phase legs as well as connection of voltage leads to each of the phase legs. It should be appreciated that such connections are often made temporarily for test purposes. Consequently, such temporary connections often require the equipment or facility to be turned off or shut down while the temporary connections are made. After the measurements are taken, the equipment or facility must then be turned off or shut down to allow the watt meter to be disconnected. Obviously, such connections or disconnections are required for taking power demand measurements are time-consuming, and also potentially dangerous.
In essentially all facilities where electrically-operated equipment is employed, there is a watt-hour meter installed at the facility between the main distribution panel of the facility and the electrical feed from the commercial power utility. The principal object of this invention is to provide an apparatus and method for measuring power demands from conventional watt-hour meters.
More particularly, watt-hour meters include a rotatable metallic disk that is caused to angularly rotate as a linear function of the energy, expressed in watt-hours, being utilized. The angular rotation of the disk drives a series of reduction gears which, in turn, causes the incrementing of a numerical display register. The meter includes a glass housing so that the rotating disk and the display register can be readily viewed. The display register reveals the total amount of energy consumed.
Historically, utility companies "read" watt-hour meters on a monthly basis in order to determine the amount of energy consumed by a particular facility during that period so that the customer can be billed appropriately. Commonly, the watt-hour meters are read by a person who visually views the display register and manually records the total amount of energy consumed by that customer since the last reading. The data is then appropriately entered and then processed by computers to generate the customer's bill. More recently, there have been various electrical systems developed for electronically reading the watt-hour meter so that data indicative of the total energy consumed may then be electronically stored or transmitted to the utility company for processing.
For example, in U.S. Pat. No. 4,638,314 entitled "Meter Transponder Hybrid", there is disclosed circuitry for counting pulses indicative of energy consumption and for transmitting such consumption data over the utility power lines to a remote location. The circuitry is mounted onto a cylindrical-shaped printed circuit board. The circuit board is dimensioned to fit around the watt-hour meter mechanism inside of the glass housing.
Similarly, U.S. Pat. No. 5,130,641 entitled "Eddy Wheel Edge Sensor" discloses a sensor positioned inside of the glass housing of a watt-hour meter for detecting the rotation of the meter's disk. U.S. Pat. No. 5,241,306 entitled "System and Method for Introducing Meter Sensor Hystersis" discloses a light emitter and sensor that detects the rotation of a watt-hour disk by means of a notch that is formed onto the disk's shaft. U.S. Pat. No. 4,491,793 entitled "Detachable Magnetic Coupler Communication Apparatus" discloses an exteriorly-mounted device that optically communicates with the electronic circuitry within the watt-hour meter.
In U.S. Pat. No. 4,792,677 entitled "System for Use With a Utility Meter for Recording Time and Energy Use", there is disclosed a sensor that is positioned within the glass housing of a watt-hour meter for detecting the rotation of the disk. A circuit is provided for processing and storing signals from the sensor for the purpose of time-stamping energy consumption. The time-stamped data is then transmitted to a central computer for processing. The customer is billed for the energy consumption based in part upon the time of day in which the energy was consumed.
In U.S. Pat. No. 4,204,115 entitled "Removably Attachable Watt-Hour Meter Monitor Device", there is disclosed a monitoring device that is affixed to or positioned opposite the glass housing of a conventional watt-hour meter. The monitoring device includes a light source and a photo resistor, with appropriate lenses for focusing and receiving the light onto the rotating disk of the watt-hour meter. The monitor device serves to count the rotations of the rotating disk for computing electrical consumption. U.S. Pat. No. 4,636,637 entitled "Method and Apparatus for Detecting Motion Through a Transparent Enclosure, with Spurious Information Detecting and Compensating Means" discloses a similar monitoring device that is affixed to the glass housing of conventional watt-hour meter for measuring energy consumption.
Finally, in U.S. Pat. No. 5,214,587 entitled "Device for Monitoring Utility Usage", there is disclosed a meter sensor assembly that is attached exteriorly to the glass housing of a watt-hour meter. The sensor assembly detects the rotation of the meter's disk through the glass housing. Sensor signals from the sensor assembly are electrically connected via a cable to a customer interface unit that displays energy consumption. A reset feature is provided that allows the resetting of the accumulated energy consumption when the utility company reads the meter. This allows the customer to compare and verify the utility company's billing statement to the total energy consumed as indicated on the interface unit.
Unfortunately, none of the known prior art systems and devices, as exemplified in the above-identified patents, are configured or utilized to measure power demand. Therefore, there presently exists a need for an apparatus and method for measuring power demands from conventional watt-hour meters.
Another object of this invention is to provide an apparatus and method for measuring power demands from conventional watt-hour meters that is operable exteriorly of the glass housing of the watt-hour meter such that power demand measurements can be quickly and easily taken without having to gain access to the inside of the watt-hour meter enclosure.
Another object of this invention is to provide an apparatus and method for measuring power demands from a conventional watt-hour meter that employs a laser scanner that accurately detects each rotation of the meter's disk, thereby being substantially unaffected by spurious light and other potential sources of interference.
The foregoing has outlined some of the pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and applications of the intended invention. Many other beneficial results can be attained by applying the disclosed invention in a different manner or modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the following summary of the invention and the detailed description of the preferred embodiment, as well as the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.